A Long Islander, charged as a teenager with plotting to join a branch of al-Qaida to battle against U.S. soldiers, was sentenced Tuesday to 13 years in prison by a judge in federal court in Central Islip.

Justin Kaliebe, now 22, was age 18 when he was arrested in January 2013 at Kennedy Airport while attempting to board a plane to travel to Yemen and fight with al-Qaida in the Arabian Peninsula,

U.S. District Judge Denis Hurley also ordered Kaliebe to serve 20 years supervised release, during which he would be barred from accessing terrorist or criminal organization websites, could not associate with jihadis, and federal officers would be permitted to search his residence.

Kaliebe faced up to 30 years in prison and a lifetime of supervised release.

Kaliebe, who has lived in Babylon and Bay Shore, pleaded guilty in June 2013 to attempting to provide material support to terrorists and attempting to provide material support to a designated foreign terror organization.

“I am not the monster the government says I am ... I never intended to hurt anyone,” Kaliebe said before he was sentenced, pleading with the judge for mercy. “I am so sorry.”

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Kaliebe’s attorney, Anthony La Pinta of Hauppauge, argued that his client should get a lenient sentence, as little as 3 years, because of his diminished capacity from a form of autism, a hormonal deficiency that delayed his growth, and he was raised in a disruptive family environment.

In imposing sentence, Judge Hurley said he took into account La Pinta’s arguments, but said Kaliebe’s willingness to go to Yemen and join al-Qaida showed that “he was a very dangerous individual.”

After the sentencing La Pinta said: “I am disappointed and feel that a lesser sentence was warranted. Justin is a harmless young man who had many psychological, medical and personal issues that contributed to his criminal conduct.”

Eastern District Assistant U.S. Attorneys John Durham and Seth Ducharme had argued that Kaliebe was fully aware of his actions and should get at least 24 years in prison. They declined to comment afterward.

Durham and Duchrme have noted that several days before Kaliebe was arrested, an undercover agent referring to his planned Yemen trip, said to him: “I want to let you know for the last time ... if you don’t want to do this, you don’t have to,” according to a court transcript. “I’m not going to be mad ... Nobody is going to be mad at you. And you could do ... other ways ... serve God the almighty.”

But Kaliebe replied, the transcript said: “I understand there is a way out, but for me, the only way out is martyrdom ... God the almighty prescribed this for me.”

Both prosecutors and defense attorney presented medical witnesses in pre-sentencing hearings to support their views.

According to court records, Kaliebe, a convert to Islam, was helped in turning to terrorism by listening to lectures on the internet that included those of Anwar al-Awlaki, an American-born cleric and influential spokesman for the organization who was killed by a U.S. drone strike in 2011.

Kaliebe was registered in the Babylon school district during 2012-13, and was enrolled in the BOCES Alternative High School program, the district has said.

An associate of Kaliebe’s, Marcos Alonso Zea of Brentwood, was sentenced to 25 years in prison in 2015 after pleading guilty to obstruction of justice and attempting to provide material support to a foreign terrorist organization.